In voice-over-Internet-protocol (VoIP) telephony systems, voice calls are digitized, assembled into packets, and then directed over Internet protocol (IP) networks instead of being sent via the Switched Circuit Network (SCN). The SCN includes networks such as the Integrated Services Digital Network (ISDN) and the Public Switched Telephone Network (PSTN). Internet technologies were originally designed to handle the transport of data resilient to delays, jitter, and retransmissions, all of which can result in packet loss. Voice and other real-time media are much more sensitive to these inevitable IP network characteristics. IP instabilities can cause gaps in voice transmission, clicks and other background noises, and distortions. Acceptable quality of service (QoS) is a major concern in VoIP.
Currently, there is no system that ensures that VoIP calls are routed with acceptable quality. What is needed is a VoIP system that checks route quality and routes VoIP calls only over routes that meet a quality criterion.